This invention relates to an automatic coating method for carrying out coating operations in various colors automatically by selectively loading and unloading paint cartridges of different colors into and from a coating apparatus, and an automatic coating apparatus therefor.
Generally, for coating objects like vehicle bodies, for example, rotary atomizing head type coating apparatus which are equipped with a rotary atomizing head have been in wide use. Lately, coating apparatus of this sort are increasingly required to meet demands for reductions of the amounts of paint and solvent to be discarded at the time of color changes and for capability of coping with a large number of paint colors.
As a first example of the prior art of this category, Japanese Laid-Open Patent Publication No. H8-229446 describes a rotary atomizing head type coating apparatus which is so arranged as to reduce the amounts of discarding paint and solvent and which can cope with an increased number of paint colors. This rotary atomizing head type coating apparatus employs paint cartridges which are filled with different paint colors and adapted to be selectively and replaceably mounted on the coating apparatus in the course of a coating operation on vehicle bodies. However, no description is given in this prior art with regard to an apparatus for changing the paint cartridges.
As a second example of the prior art, there has been known an automatic coating apparatus (e.g. from Japanese Laid-Open Patent Publication No. S63-175662) which is arranged to perform a coating operation automatically according to programmed procedures. According to this prior art automatic coating apparatus, paint cartridges of various colors are located within a working area of a coating robot or other working mechanism, and, at the time of cartridge replacement, the working mechanism is operated to serve as a cartridge changer. Therefore, in this case each one of the paint cartridges needs to be located within a reach of the working mechanism. However, actually there is a limit to the number of paint cartridges which can be located within a working area of a working mechanism.
Further, as a third example of the prior art, there has been known an automatic coating apparatus as described in International Gazette WO97/34707. This third prior art coating apparatus is comprised of a working mechanism such as a coating robot which is provided in a coating area, a coating machine which is mounted on the working mechanism and provided with a rotary atomizing head adapted to be put in high speed rotation by an air motor for atomizing paint into finely divided particles, a number of paint cartridges which are filled with paint of different colors and adapted to be replaceably mounted on the coating machine, and a cartridge changer which is arranged to support the respective paint cartridges and mount and dismantle a paint cartridge on and from the coating apparatus for cartridge replacement.
In this case, the cartridge changer is provided with a round support table which is arranged to support a large number of paint cartridges in an annular array. The cartridge support table is turned by a drive motor or the like to bring a paint cartridge to be used for a coating operation, to a predetermined pick-up position.
In the case of the third prior art automatic coating apparatus which is arranged in the manner just described, paint is supplied from a cartridge to a coating machine of the coating apparatus to spray the paint toward a coating object. At this time, the working mechanism is put in operation to move the coating apparatus along contours of coating surfaces of a coating object.
When changing the paint color, the working mechanism is moved to bring the paint cartridge on the coating apparatus to a predetermined cartridge changing position of the cartridge changer. Then, a cartridge gripper which is provided on the side of the cartridge changer is operated to remove a consumed or empty paint cartridge from the coating apparatus and return same to the cartridge support table. Nextly, a fresh paint cartridge which is filled with a next color is picked up from the cartridge support table and mounted on the coating apparatus.
The cartridge changer according to the prior art just mentioned is arranged to locate a selected one of the paint cartridges on the cartridge support table in a predetermined pick-up position by turning the support table, and mounted on the coating apparatus in place of a cartridge of a previous color.
However, the cartridge support table, which carries a large number of paint cartridges in an annular array, is necessarily large in size and weight. It follows that, for driving the cartridge support table, the cartridge changer is required to have a drive motor with large driving power. Needless to say, a cartridge changer of a large size is disadvantageous in that it invites increases in cost.
In view of the above-mentioned problems with the prior art, it is an object of the present invention to provide an automatic coating method and apparatus for putting the method into practice, in which a large number of paint cartridges of different colors are arranged and located in such an efficient manner as to facilitate cartridge replacements and to realize reductions in size and cost of the coating apparatus in addition to improvements in working efficiency.
In order to achieve the above-stated objective, according to the present invention, there is provided an automatic coating method which is applied by the use of a working mechanism located in a coating area, a coating apparatus mounted on the working mechanism and adapted to be replaceably loaded with paint cartridges of various colors, and a cartridge changer including a paint replenishing means for replenishing paint into the paint cartridges and a cartridge gripper means having a couple of gripper members for gripping paint cartridges separately thereon and adapted to hand over paint cartridges to and from the coating apparatus to replace an empty paint cartridge on the coating apparatus by a replenished paint cartridge.
The automatic coating method according to the present invention comprises: coating step of coating object by the coating apparatus loaded with a replenished paint cartridge and moved by the working mechanism; a replenished paint cartridge picking up step of picking up said replenished paint cartridge of a color to be used in a next coating operation from a paint replenisher means by the use of one of the gripper members of the cartridge gripper means; an empty paint cartridge unloading step of unloading said empty paint cartridge from the coating apparatus by the use of the other one of the gripper members of the cartridge gripper means having the replenished paint cartridge still gripped in one gripper member; the replenished paint cartridge loading step of loading said replenished paint cartridge into the coating apparatus by one gripper member of the cartridge gripper means having the empty paint cartridge still gripped on the other gripper member; and returning the unloaded empty paint cartridge to the paint replenishing means.
With the arrangements just described, in the coating step, the working mechanism is put in motion to perform a coating operation by the coating apparatus which is loaded with a replenished paint cartridge. In the step of picking up a replenished paint cartridge, a replenished paint cartridge is gripped and picked up from the paint replenishing means by one of the gripper members of the cartridge gripper means. Nextly, in the empty cartridge unloading step, the empty paint cartridge is picked up from the coating apparatus by the other gripper member of the cartridge gripper means while gripping the replenished paint cartridge by one of the gripper members of the cartridge gripper means. In the replenished paint cartridge loading step, the replenished paint cartridge is loaded into the coating apparatus by one of the gripper members of the cartridge gripper means while gripping the empty cartridge by the other gripper member of the cartridge gripper means. Thus, in the empty cartridge returning step, a replenished paint cartridge and an empty paint cartridge are exchanged between the coating apparatus and the cartridge changer.
According to the present invention, there is also provided an automatic coating apparatus suitable for putting the above-described method into practice, which basically includes a working mechanism located in a coating area, a coating apparatus mounted on and moved by the working mechanism and adapted to be replaceably loaded with paint cartridges of various colors, and a cartridge changer arranged to hand over paint cartridges to and from the coating apparatus to replace an empty paint cartridge on the coating apparatus by a replenished paint cartridge.
The cartridge changer used in the automatic coating apparatus according to the present invention comprises: a paint replenishing means having a number of paint replenishers correspondingly for different paint colors, each adapted to support and replenish a paint cartridge of a corresponding color; a cartridge transfer means arranged to transfer paint cartridges in the directions of three perpendicularly intersecting axis; and a cartridge gripper means supported on the cartridge transfer means and adapted to grip and transfer paint cartridges between the coating apparatus and the paint replenishing means.
With the arrangements just described, upon finishing a coating operation, the coating apparatus with an empty paint cartridge is located at a cartridge replacing position, whereupon the cartridge means is actuated to move the cartridge gripper means toward that position. At this time, the cartridge gripper means is operated to transfer and exchange an empty paint cartridge and a replenished paint cartridge of a next color between the coating apparatus and the paint replenishing means. Besides, in preparation for use in a next coating operation, the empty paint cartridge which has been handed over to and set on the paint replenishing means is replenished with paint concurrently with a coating operation by the coating apparatus.
The coating apparatus to be used in the present invention is preferably constituted by a cartridge mount portion to be replaceably loaded with paint cartridges, and a coating machine with a rotary atomizing head for atomizing and spraying paint supplied from a paint cartridge loaded in the cartridge mount portion.
With the arrangements just described, as soon as paint is spurted out from a paint cartridge which is loaded in the cartridge mount portion, it is atomized into finely divided particles and sprayed toward a coating object by the rotary atomizing head of the coating machine.
Further, preferably, the paint cartridges to be used in the present invention are each constituted by a container to be filled with paint, and a feed tube extended axially from one end of the container, and the paint replenishing means is adapted to replenish paint into the container of the paint cartridge through a fore end of the feed tube.
With the paint cartridge construction just described, paint can be replenished into the container of a paint cartridge which has been handed over to and set on the paint replenishing means, thereby utilizing the fore end of the feed tube as a replenishing port.
In this instance, preferably, the paint cartridges are each constituted by a container to be filled with paint and a feed tube axially extended from a fore end of the container, and the paint replenishing means is constituted by a plural number of replenishing stools for replenishment of various paint colors, each having a feed tube passage hole formed axially therein to receive the feed tube of a corresponding paint cartridge, and a connector member located in the replenishing stool located in a deeper position than the feed tube passage hole to connect the fore end portion of the feed tube to a paint supply passage.
With the arrangements just described, when an empty paint cartridge is returned to a replenishing stool, the feed tube of the cartridge is inserted into the feed tube passage hole on the side of the stool until its fore end is connected to the connector member for communication with the paint supply passage. Therefore, paint which is supplied to the paint supply passage is replenished into the container via the connector member and the feed tube.
Further, preferably the cartridge transfer means to be used in the present invention is constituted by a first transfer mechanism arranged to move the cartridge gripper means in a longitudinal or transverse direction of the paint replenishing means, a second transfer mechanism arranged to move the cartridge gripper means in a transverse or longitudinal direction, and a third transfer mechanism arranged to move the cartridge gripper means in a vertical direction, and the cartridge gripper means is supported on the third transfer mechanism.
With the arrangements just described, the cartridge gripper means is moved in longitudinal, transverse and vertical directions by the first to third transfer mechanisms and located in the cartridge replacing position or in a cartridge pick-up position over a selected one of paint cartridges which are supported on the paint replenishing means. In addition, the cartridge gripper means is moved vertically up or down by the third transfer mechanism at the time of lifting up or lifting down a paint cartridge from or onto the coating apparatus or paint replenishing means.
Further, preferably the cartridge gripper means to be used in the present invention is provided with a couple of gripper members side by side to grip a couple of paint cartridges separately and independently of each other.
With the arrangements just described, a replenished paint cartridge is gripped in one of the gripper members of the cartridge gripper means at the time when an empty paint cartridge is unloaded from the coating apparatus by the other one of the gripper members at the time of replacement. Therefore, the replenished paint cartridge can be loaded into the coating apparatus immediately after removal of the empty paint cartridge.
Further, according to the present invention, the cartridge changer is provided with a shock absorber provided between the cartridge transfer means and the cartridge gripper means to permit movements of the cartridge gripper means relative to the cartridge transfer means when brought into abutting engagement with a paint cartridge.
With the arrangements just described, when the cartridge gripper means is moved toward and abutted against a paint cartridge by the cartridge transfer means, the shock absorber permits the cartridge gripper means to move for buffering the impacts of abutment.
Further, according to the present invention, the automatic coating apparatus further comprises a washer means which is located in the vicinity of a cartridge replacing position of the cartridge changer for washing the coating apparatus each time when replacing an empty paint by a replenished paint cartridge of a different color.
With the arrangements just described, when the coating apparatus is located in a cartridge replacing position for cartridge replacement, deposited previous color on the coating apparatus can be washed off by the washer.